class_docstr: A helper class that represents input string that to be modified.
  
  Text that Sample contains parsed in data set,
  ``TextField`` provides multiple methods for Sample to modify.
  
  Support sentence level and word level modification,
  default using word level API.
docstr: Get pos tag of given index.
  
  :param int desired_word_idx: desire index to get pos tag
  :return:  pos tag of word of desired_word_idx.
docstr_tok: ["Get","pos","tag","of","given","index",".",":","param","int","desired_word_idx",":","desire","index","to","get","pos","tag",":","return",":","pos","tag","of","word","of","desired_word_idx","."]
code: def pos_of_word_index(self, desired_word_idx):
      r"""
      Get pos tag of given index.
  
      :param int desired_word_idx: desire index to get pos tag
      :return:  pos tag of word of desired_word_idx.
  
      """
      if (desired_word_idx < 0) or (
          desired_word_idx > len(self.field_value)
      ):
          raise ValueError(
              f"Cannot get POS tagging at index {desired_word_idx}"
          )
  
      return self.pos_tagging[desired_word_idx]
  
imports: from .field import Field
  from ....common.utils.list_op import *
  from ....common.preprocess.en_processor import EnProcessor
  from ....common.settings import ORIGIN, TASK_MASK, MODIFIED_MASK
label_desc: Use image node_id 7 for calling the TextField obj's underlying member method code with example usage: obj.pos_of_word_index(desired_word_idx) and returns: self